In many processes for analyzing samples, particularly in batch and serial processes where several samples are involved, it is desirable to improve throughput by providing a greater degree of automated control over various stages of the sample handling, preparation, and analysis processes and by providing better management of sample-related data. In one aspect, instrumentation for the handling, preparation and analysis of samples has become more automated. For instance, automated sample handling systems have been developed that include one or more trays holding arrays of vials, test tubes, or multi-well plates containing small quantities of liquid samples. These systems typically include a sampling needle that can be programmed to move to each vial in order to dispense samples into the vials or aspirate samples from the vials. Alternatively, the vials or trays holding the vials may be moved to a sampling needle or other component of the sample handling system. In another aspect, steps have been taken to improve the identification of individual samples. Improvements in sample identification have primarily been made through the utilization of barcode scanning systems. Barcode scanning systems employ an optical barcode scanner that reads a barcode printed on a label. The barcode consists of a combination of dark parallel bars and light spaces between the bars. The barcode scanner reads the barcode by directing a beam of light at the barcode. Because the dark bars of the barcode absorb light and the light spaces reflect light, a detector in the barcode scanner can receive the reflected light signals and convert them into electrical signals, which thereafter can be recognized by electronic means as characters. Barcode labels have been applied to vials and, in the case of multi-well plates, a single barcode label has been applied to a plate.
While barcode systems and other optical techniques may be useful in such applications as the tracking of consumer goods, these types of systems present problems when applied to procedures for handling small liquid-phase samples in conjunction with analytical techniques. The information represented by a barcode is quite limited and fixed. The barcode typically constitutes a short series of characters such as those corresponding to the well-known Uniform Product Code (UPC). Due to the brevity of these character sets, the barcode is capable of identifying only the type of sample or the tray or group of samples of which the sample is a part. When a large number of individual samples are to be handled and analyzed, each of which may be different from the others in terms of composition or other parameters, there are not enough characters in a barcode to adequately distinguish one given sample as being unique from another sample. Even if a barcode were to be employed to uniquely identify a sample as being, for example, Sample #1, that same barcode cannot be used to provide any additional information about that particular sample.
Moreover, because a barcode system depends on optics, it is orientation-sensitive; that is, there are only a finite range of angles between a barcode and a barcode scanner over which optical communication will be successful. When applied to sample handling and analysis systems, the barcode system often requires that several barcode scanners be located at various points along the system in order to adequately track the sample, or that a given barcode-containing vial be transported to a single barcode scanner. Additionally, again due to the use of optics, a barcode-containing vial must be precisely positioned in relation to a barcode scanner to ensure that no other object will interfere with the light path, including neighboring vials. Another related problem stems from the fact that an optical path is easily modified by the presence of substances commonly encountered in sample handling. The smearing of the printed barcode through contact with a researcher or an object, the marring or degradation of the barcode by solvents or other substances, or simply the obstructive presence of fluids or particles on the barcode, all may destroy the ability of the barcode to be accurately read by a barcode scanner.
In view of the foregoing, it would be advantageous to provide a means for uniquely identifying vials and other types of sample containers without the problems attending barcode technology and other known techniques employed in conjunction with sample preparation, handling, and/or analysis. The ability to read an identification code as the vial is accessed for sampling or mixing operations, without moving the vial to another position, would also present significant advantages, in terms of time and chain of custody-type concerns.